1. Field of the Invention
The present invention relates to a charged-particle beam drawing tool, and, more particularly, relates to a correction system, a correction method, a program for correcting a deflection distortion by a deflector and a method for manufacturing a semiconductor device.
2. Description of the Related Art
As integrated circuits have become finer and have higher density, charged-particle beam drawing tools using a charged-particle beam, such as an electron beam (EB) or a focused ion beam (FIB), are becoming more important. A charged-particle beam drawing tool, as a semiconductor manufacturing device, is required to achieve stable operation, a high rate of throughput, and a fine-processing capability. However, there is a limit to the precision with which parts constituting the charged-particle beam drawing tool are processed and assembled. Accordingly, a deflection distortion may be caused by a deflector for deflecting a charged-particle beam. When a charged-particle beam is deflected, there are some cases where the deflection distortion causes an aberration between a position which is actually illuminated by the charged-particle beam and a position expected to be illuminated at a design stage. In order to direct a charged-particle beam with high accuracy, it is important to correct the deflection distortion due to the deflector.
As a correction method in a charged-particle beam drawing tool, a method is employed in which a correction value for correcting the deflection distortion is calculated, and a deflection voltage equivalent to the correction value is fed back to a deflector. As a method of calculating the correction value, for example, a deflection area on a stage to which a charged-particle beam is deflected is virtually divided into equal blocks in a matrix. A correction coefficient of a correction formula for correcting a deflection distortion is calculated for each of the equal blocks, and a correction value is calculated based on the correction formula using the correction coefficients.
However, the distribution of an electrical field or a magnetic field formed by a deflector is likely to become less even as the field is farther from an optical axis of the deflector. Accordingly, deflection distortion has a tendency to increase as a charged-particle beam becomes farther from the optical axis. The method in which the deflection area is equally divided results in the correction accuracy being decreased as the deflection area becomes farther from the optical axis. In this connection, a method in which a deflection area is virtually divided into equal small blocks can be also considered in order to achieve high accuracy, even at a position far from an optical axis. However, the method in which the deflection area is divided into equal small blocks requires an enormous amount of time to provide a correction for each of the equal small deflection blocks. As a result, the throughput decreases. That is, there is a trade-off relation between the accuracy with which the deflection distortion is corrected and the time required to correct the deflection distortion.